1. Field of the Invention
The invention concerns a metal housing for an electrical connector particularly suitable for cables including a conductive braid covered with insulation, the braid surrounding at least one insulated electrical conductor and providing a screen against electromagnetic interference.
2. Description of the Prior Art
It is known to protect the end of the cable, when connected to a connector, by providing the connector with a metal housing. This is electrically connected to the braid and to a metal chassis carrying a socket into which the connector is inserted. It is also known to use a metal-coated plastics material housing which is lighter in weight and less costly than an entirely metal housing. To achieve good protection it is essential that the electrical contact resistance between the braid and the housing is extremely low.
French patent application 2 576 457 describes a metal housing for an electrical connector particularly suitable for a cable having a single braid surrounding a plurality of insulated electrical conductors. A length of the end portion of the braid is stripped and covers a first tube which is accommodated between the braid and the insulation covering the conductors. A second tube outside the braid covers its end portion. The second tube is made from copper, for example. It is crimped to fasten together the two tubes and the braid. The first tube is attached to the housing and the braid is therefore fixed firmly to the housing and the electrical contact resistance between the housing and the braid is very low.
A disadvantage of this type of housing is that fitting it requires a relatively large number of operations: one operation to strip the braid; one operation to fit the first tube between the braid and the insulation; one operation to fit the second tube around the braid; and a crimping operation. Also, this type of housing is not suitable for connecting a plurality of small cables each comprising an individual screening braid.
Other known types of housing include a rubber ring, or a spring ring, clamped by a sort of nut, to press the screening braid of a cable against a part of the metal housing, this part usually being conical in shape. Another known type of housing includes an orifice through which the cable is passed and having a plane part against which the cable is pressed by a collar. If the cable incorporates a screening braid the latter is stripped in line with the orifice of the housing to make electrical contact with the housing at the point where the collar clamps the cable against the housing. All these known housing types have the disadvantages of requiring the braid to be stripped and of incorporating bulky clamping means.
U.S. Pat. No. 4,533,199 describes a connector in the form of a single piece of plastics material comprising two generally plane parts articulated by a flexible hinge. A first part carries contacts each in the form of an insulation-displacement fork with the major axis perpendicular to the plane of the first part. The second part carries bosses. This connector can be used to connect a plurality of cables each comprising a screening braid and an insulated interior conductor. The cables are disposed in flat bundles and each is connected to two adjacent insulation-displacement forks. One fork makes contact with the braid through the insulation covering the braid and one fork makes contact with the interior conductor through the insulation covering this conductor, the braid and the exterior insulation being removed near the end of the cable.
The cables are pressed into the fork by closing the two articulated parts together, each cable being pressed into its fork by bosses on the second part of the connector. The connector is held closed after this operation by a latching device which is an integral part of the connector and comprises two lugs which snap into place in two apertures.
A particular advantage of this connector is that it is compact and can be used to connect a plurality of cables each comprising an individual screening braid. The connection to each braid does not require any stripping of the cable. On the other hand, this connector has the disadvantage of not providing any screening of the end of each cable. External interference can therefore affect the conductors through the plastics material. Also, interference may arise from radiation from the ends of adjacent cables, within the connector itself.
The object of the invention is to propose a compact housing which protects the ends of the cables against external and internal electromagnetic interference and which can be fitted without stripping the screening braids. The invention consists in a metal housing comprising two facing half-housings hinged together and incorporating orifices provided with projections in the form of forks constituting insulation-displacement contacts for electrically connecting the housing to the screening braid of each cable by the simple action of closing the two half-housings by rotation about the hinge axis.